A betrayal. A sellout. Like closing Massachusetts General Hospital’s emergency room to the public, said a former Mass. General anesthesiology chief who has been taking violin lessons in the continuing studies program of the Longy School of Music of Bard College.

The harsh comments have come in the past week from teachers and parents upset by Longy’s decision to stop offering music lessons and classes to children and amateur adult players. The school’s move, announced via e-mail March 6 and effective at the end of August, has sent controversy tearing through Boston’s music community.

Parents and teachers have picketed each of the last two Saturday mornings on Longy’s campus, an online petition has gathered more than 1,000 signatures, and the faculty union has complained to the Cambridge City Council. On Wednesday, the council’s University Relations Committee will meet to discuss Longy.

At the heart of the dispute are differing visions for the nearly 100-year-old institution: Is the school’s primary role to offer music programs for the general public, through its preparatory and continuing education programs? Or, as argued by Longy’s board, should the school’s focus be on its full-time conservatory students?

“The message is that I think our own local community doesn’t actually know Longy,” said Longy’s president, Karen Zorn, who believes that the school has been clearly moving toward the focus on the conservatory for some time.

One thing is clear: The Cambridge campus isn’t big enough for both the 215 full-time enrolled conservatory students and the 700 children and 200 adults participating part time at Longy, she said.

Pianist Alexander Morollo, 24, who is in the school’s degree program, said it’s common to find conservatory students practicing in the hallways and closets. Recently, he spotted signs put up by the school telling students not to practice in bathrooms. As a pianist, Morollo doesn’t have that option. Instead, he often heads to Boston University late at night. A friend lets him into a music studio and he practices in the early morning, heading home after the MBTA trains start running.

‘None of us wanted to do this. But the logic was really overwhelming; we had to do this.’

“I know that it’s difficult to find practice rooms at any conservatory, but just walking around the school, it was kind of shocking” when he arrived at Longy, Morollo said.

The announcement that children’s and continuing adults’ classes would end caught even local music insiders off guard.

“I was not expecting it at all,” said New England Conservatory’s president, Tony Woodcock, who said he would wait to offer an opinion until he’s talked with Zorn.

Nina Totenberg, the National Public Radio correspondent whose late father, Roman, was a director of Longy, said she was unhappy with the school.

“I know all of the players in this,” she said. “I know the faculty. I’ve known [Bard College president] Leon Botstein from the time he was a little boy. And I have the highest regard for them all. But this makes me very sad, and I don’t really feel Longy has played entirely straight with the community.”

Alexandra Moellmann, whose two children have studied at Longy, called the decision “a betrayal” in an e-mail she circulated. Several others associated with the school criticized what they called Bard’s “sellout” of Longy.

In explaining the decision, Longy’s leaders stressed the space crunch and the school’s financial challenges.

When she arrived, in 2007, Zorn said, Longy ran a roughly $1 million deficit on its $7 million annual budget. Full-time students currently pay a little over over $30,000 in yearly tuition. Those enrolled in the prep and continuing studies programs pay a range in tuition, but a private half-hour weekly lesson generally costs around $1,600 per academic year. The nondegree programs command nearly 50 percent of the available instruction space, Zorn said, yet generate only 25 percent of the school’s revenue.

What’s more, as the conservatory program grows — there were about 100 full-time students a decade ago, more than double that now — demand for practice space has increased.

The school could not continue in its current situation, said Rob Straus, a psychologist who is a member of Longy’s board of governors. “We had to, just to stay alive as a school, make a preference for the conservatory,” Straus said. “None of us wanted to do this. But the logic was really overwhelming; we had to do this.”

Zorn’s tenure has been marked by change and conflict. In 2010, she restructured the school’s part-time faculty, cutting 37 of its 188 teachers. This led to tension with many faculty members, who formed a union.

Some believe that those who have spoken against changes have been forced out.

“You can’t believe anything they say,” said violinist Clayton Hoener, president of the faculty union, of Longy’s leaders.

Others believe Zorn has stabilized Longy.

“Karen came in, she rescued the school from bankruptcy and realized she had to pare down,” said Anna Gabrieli, a voice teacher for 15 years. “Some of these teachers, they’ve been so vitriolic and difficult.”

Just last year, Zorn and Bard president Botstein finalized plans to merge the two schools. That’s led many to believe Botstein, a conductor and educator, is driving the decision.

“Longy just gave the school to Bard,” said Warren Zapol, the former Mass. General anesthesiology chief. “It’s a takeover by another institution, no matter what they say.”

Under the terms of the merger, Longy is now part of Bard, though Botstein and Zorn said that is to encourage creative partnerships and Longy maintains its financial and administrative independence.

“We had no role in the decision” to cut the preparatory programs, Botstein said. He said he is disappointed by the attacks on Zorn and Longy.

“Am I upset by people believing fictions? Yeah,” he said. “That’s the same problem with people believing evolution isn’t true. There is a truth, and there is fiction. And the truth is that Longy runs autonomously. We never took them over.”

As Zorn stresses, the issue isn’t only about space and money. Longy, she said, wants its program to distinguish itself by focusing on training musicians to work in underserved communities. Longy has students working in schools in Dorchester, Somerville, Brighton, and Cambridge.

Other area music schools, she said, can offer more general education: NEC, South Shore Conservatory, Suzuki School of Newton, Concord Conservatory of Music, and New School of Music in Cambridge.

Alyssa Lee, executive director of the New School, said calls began to come in after Longy’s announcement. Her board has met to discuss how many children can be accommodated.